Today large parts of Eastern Europe can be considered as strikingly species-poor "agrarian-deserts". Nevertheless, the region also retains relatively large areas of species-rich farmland. Changes in the weed flora in this region, with special regard to the disappearing weed species, is the subject of relatively small numbers of international scientific studies compared to the western part of Europe. The average weed species number per plot seems to have declined less in eastern than in western countries since the Second World War. However, by the turn of the Millennium the number of threatened weed species had increased considerably, which is apparent in the recently updated national weed red lists. Many studies indicate that lower farming intensity and diversified farming systems at higher altitudes provided better conditions for the occurrence of rare species and greater diversity than intensively farmed lowlands. Unfortunately, only a few traditionally managed small fields remain in extreme habitats, and they are continuously being abandoned. Regrettably, Eastern Europe mostly lacks any conservation initiatives which directly target the preservation of rare and threatened arable weeds, consequently further declines are anticipated.